linux-kernel - Re: [PATCH] x86/PCI: initialize PCI bus node numbers early

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Message-ID: <4A57A1FE.30609@kernel.org>
Date:	Fri, 10 Jul 2009 13:18:06 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
CC:	linux-kernel@...r.kernel.org,
	Jesse Brandeburg <jesse.brandeburg@...il.com>
Subject: Re: [PATCH] x86/PCI: initialize PCI bus node numbers early

Jesse Barnes wrote:
> The current mp_bus_to_node array is initialized only by AMD specific
> code, since AMD platforms have registers that can be used for
> determining mode numbers.  On new Intel platforms it's necessary to
> initialize this array as well though, otherwise all PCI node numbers
> will be 0, when in fact they should be -1 (indicating that I/O isn't
> tied to any particular node).
> 
> So move the mp_bus_to_node code into the common PCI code, and
> initialize it early with a default value of -1.  This may be overridden
> later by arch code (e.g. the AMD code).
> 
> With this change, PCI consistent memory and other node specific
> allocations (e.g. skbuff allocs) should occur on the "current" node.
> If, for performance reasons, applications want to be bound to specific
> nodes, they should open their devices only after being pinned to the
> CPU where they'll run, for maximum locality.
> 
> Any thoughts here Yinghai or Jesse?
> 
> 
>  include/asm/pci.h |    2 +
>  kernel/setup.c    |    2 +
>  pci/amd_bus.c     |   61 +-----------------------------------------
>  pci/common.c      |   77 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 83 insertions(+), 59 deletions(-)
> 
> Thanks,

could use

static int mp_bus_to_node[BUS_NR] = {
        [0 ... BUS_NR - 1] = -1
};

so we avoid to add pci_bus_to_node_init()

YH
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